In a hub unit for a driving wheel, a hub and an inner ring are supported to be rotatable on the inner diameter side of an outer ring of a bearing through a plurality of rolling members.
The outer ring is fixed to a knuckle constituting a suspension system by means of a supporting flange provided on the outer peripheral surface thereof. A plurality of outer ring tracks are provided on the inner peripheral surface of the outer ring, and the hub and the inner ring are supported on the inner diameter side of this outer ring.
The hub is provided with a mounting flange for mounting a wheel in the outer edge portion thereof. A first inner ring track is formed in a middle part of the outer peripheral surface of the hub, and the inner ring is fixedly fitted on a small-diameter step portion of the inner end portion of the hub. This inner ring is formed with a second inner ring track. In a central part of the hub, in case, for example, of a hub unit for a driving wheel, there is provided a female spline for bringing a constant velocity universal joint into spline-fitting to secure.
Also, there is a hub unit with a sensor for detecting a speed of rotation of a vehicle, in order to support a wheel to a suspension system to be rotatable and also to control an antilock brake system (ABS) or traction control system (TCS).
When this hub unit is used, a magnetic encoder which is fixed to the inner ring and is magnetized with a plurality of north poles and south poles alternately in the peripheral direction is rotated upon rotation of the wheel, and an output of the sensor which is provided to face the magnetic encoder is changed. Since the frequency of this output change is proportional to the speed of rotation of the wheel, an output signal of the sensor is inputted to a control unit through a harness to obtain the speed of rotation of the wheel, thereby appropriately controlling the ABS or the TCS.
Note that conventional examples related to the above-described prior art are disclosed in Japanese Patent Laid-Open Application Nos. 2000-221202, 2000-221203 and 2000-221204 which will be described later.
Incidentally, such a hub unit as of the type described above is, after the magnetic encoder or the like has been mounted on the inner ring of the bearing, transported as a unitary hub unit, and thereafter, the outer ring thereof is thread-fixed to a knuckle of the car body with bolts or the like in an assembly process of the car. Thus, the hub unit is mounted on the car body side.
However, in case of the hub unit for the driving wheel, it is arranged such that the sensor for detecting a speed of rotation of the wheel is conventionally mounted on the side of the knuckle of the car body.
Accordingly, it is required to examine whether or not a positional relationship between the sensor for detecting a speed of rotation on the knuckle side of the car body and the magnetic encoder on the hub unit side is appropriate and to adjust it. As a result, the assembling and adjusting processes become complicated.
For these reasons, there is a demand that the sensor for detecting a speed of rotation should also be mounted on the hub unit side in advance, like the magnetic encoder.
However, since the constant velocity universal joint is provided on the inner side of the hub unit in the car width direction, a space for mounting the sensor is comparatively small, so that it is difficult to mount the sensor for detecting a speed of rotation on the hub unit side, and moreover, it is very troublesome to arrange the harness which is extended from the sensor or to prevent interference thereof with the constant velocity universal joint.
Particularly, a code (a harness or a connector) for connecting the sensor is extended out of the knuckle through a hole drilled in the knuckle. However, since the knuckle has to be drilled, the strength of the knuckle is reduced, and the size or the weight of the knuckle may be increased to compensate the reduction. Also, though a space between the knuckle and a constant velocity universal joint CVJ is sufficiently secured conventionally so as to prevent interference by the harness or the connector, the size or the weight of the knuckle may be increased in order to secure such a space for preventing interference by the harness or the connector.
Further, the internal circuit of the sensor is disposed linearly and is sometimes placed out of the cap. Since the sensor is placed out of the fitting diameter of the outer ring as the internal circuit is disposed linearly, it is required to drill the knuckle, or to form a cut-away portion on the knuckle, or to make some similar preparations, which may resultantly decrease the strength of the knuckle. Also, since a space for preventing interference by the harness or the connector is required when the internal circuit is disposed linearly, the size or the weight of the knuckle may be increased.
The present invention has been contrived taking such circumstances as described above into consideration, and an object thereof is to provide a hub unit for a driving wheel which is provided with a sensor for detecting a speed of rotation and can be mounted on a knuckle very easily in an appropriate manner.